Many modern wireless and cabled data communications systems use Orthogonal Frequency Division Modulation (OFDM). Given a fixed RF transmit bandwidth, OFDM has data bandwidth advantages over other modulation techniques. In OFDM, data bits are mapped into data symbols. A number of symbols are then grouped into a packet. Each symbol in a packet is then modulated onto a unique orthogonal carrier. The OFDM signal is therefore a sum of multiple carrier sinusoids. When combining multiple sinusoids, high peak power relative to average power is produced. Signals with a high peak-to-average ratio make signal amplification difficult. If peak power is compressed or clipped during amplification, two problems result. First, bandwidth of the transmitted signal increases causing interference in neighboring frequency channels. Signal bandwidth must meet limitations set by governmental regulatory bodies. Second, inter-symbol-interference (ISI) is induced into the modulation increasing link bit error rate.
All communication systems are designed to tolerate some degradation in modulation. However a need presently exists to reduce the peak-to-average ratio of an OFDM signal while controlling the amount of induced inter-symbol interference (ISI). If these two goals can be achieved both RF bandwidth and bit error rate limits can be met.